EAST AFRICAN SUCCULENTS.

Part 1.

By P. R. O. BALLY.

Succulents have become more and more popular with theamateur gardener during the latter years; at home they are beingincreasingly grown in hothouses, or, on a small scale, they adornmany a sheltered window.si1l. In warmer climates, where theyneed less protection from the severity of rain and cold, Succu­lents do very well in rock-gardens.

East Africa has climatic conditions which especially favourthe cultivation of Succulents-except in the higher altitudesabove 6,000feet or in those rare districts with regular, heavy,rainfalls ..

Many amateur gardeners take great pains to import· Cactiand other Succulents fromAroerica and from South Africa; theyseem to be quite unaware of the fact that East Africa possessesawealth of beautiful indigenous Succulents which can well beareomparison with any of the imported plants ..

With its-IDOdestrequirements with regard to rainfall and tosoil conditions, the Succulent garden is often the only patch ofglorious abundance and of gay colours in the listless lull of thedry season, for Succulents will thrive where most other plantswould die of starvation or of exposure..

What, exactly, are Succulents? The term is used commonlywithout diseriminatlon along with that of "Cacti" in order todesignate all fleshyplants covered with spines. This is a mistake,for the term "Cactus 'I (plural" Cacti," a latinized word derived

from the Greek noWl II kaktos," the spiny cardoon) applies tomembers of one family of plants only, theCACTACEAE, most ofwhich have indeed evolved into fleshy, leafless shapes,'which arecovered with clustets of spines. A few members of the Cactusfamily however, .like the Genus Peireskia, do not look like trueCacti at all; they are woody, spiny, shrubs with fairly large,ordinary leaves; the expert only, who studies the anatomicalcharacter of their flower, knows that they belong to the Cactaceae.

The term "Succulents" has a much wider significance(" succulent" stands for" juicy," and it is derived from the Latinnoun II succus," juice). It includes all plants which havedeveloped a capacity for storing water in various parts of theirframe, regardless of their place in the natural plant system.Thus it is correct to say that the fleshy Cacti are Succulents,but it is a mis-statement to call all Succulents: Cacti.

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PLATE 7.

FIG. 1. FIG. 2.

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Typical representatives of succulent forms; for explanation vide text.

Strictly speaking, beets, potatoes, onions and all other plantswith bulbous and tuberous roots should also be termed Succu­lents, but for practical purposes the meaning of the term hasbeen limited to such plants as store their reserve of moisture inany part of their structure showing above ground, and which~by reason of this capacity-assume strange and bizarre shapeswhich set them definitely apart from the bulk of the so-callednormal vegetation.

Storage of water becomes necessary where its supply isirregular or lacking for long periods, where the soil is porous orscarce, and where evaporation is high. As might be expected,Succulents are found mostly in arid districts, on rocks, in deserts,aJld in other localities presenting similar conditions, which are.found sometimes even at high altitudes.

Most Succulents possess acomparatively weak and small rootsystem and they are thus unable to penetrate deep down into themoisture-laden strata from which the surrounding desert vegeta­tion may draw during the greater part of the year.

They must needs make up for this deficiency by some otherquality in order to survive, and this quality is precisely thestorage of water against the long periods when .it is not availableto them from extraneous sources .. They have thus emancipatedthemselves to such an extent that they subsist where no subsoilwater is present and where other types of vegetation will not live.

Some Succulents have developed the facl,llty of survivalwithout external water supply to a point which is truly astound­ing. Most will live. on for months, some for years. True, weare conversant with this phenomenon in the case of bulbs, tubers,even with our common potato; but these are well defined centresof growth, while with most Succulents the power to survive isinherent in all part~ of the plant independently and in variousdegrees; a single leaf of Bryophyllum for instance will give riseto do.zens of young plants ..

At the beginning of last year I despatched a consignment ofsucculent Euphorbieae-mostly small cuttings and a few imma­ture plants--all packed in a dry state, wrapped up in paper;although the consignment had been under way for well over twomonths, on~y four out of seventy-five died during that period.

Cuttings of a Synadenium-which I had left tied up in abundle in a dry corner of the botanical room at the Museum,started to develop shoots and leaves after a period of apparentdeath of fully eight months, and without any visible prove<::ation.

The most astounding example of the surviving power of aSucculent I have come across in the Berlin Museum: a seeminglydead plant of Hbushman's candle" (Saraocaulon rigidum,

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GERANIACEAE) from South-West Africa had been kept therelocked up in a drawer for an unknown period, but certainly forseveral years. It was then placed into a show case at theMuseum, and, after having been an exhibit under gl~ss for threefurther years, it started to emit young shoots. Transferred to thehot-house, the plant continued to develop normally, seeminglynone the worse for its long period of apparent death. Incredibleas this may seem, in the habitat of this plant periods of droughtof seven years have been recorded. The" bushman's candle "with its poorly developed root system and with little facilitiesfor absorption of the heavy dews which occur in the desertdistricts of South-West Africa, is thickly covered with a layer ofresinous wax which is completely impermeable and which thuskeeps its vital parts effectively protected against evaporationuntil conditions provide periods-rare and brief they are-whichpermit of the development of tiny leaves and of its propagatoryorgans.

It is a curious fact that Succulents which belong to entirely ­different families and which are thus by no means related, oftenassume an outward resemblance which makes it difficult to tellthem apart.

A botanist who had travelled extensively in Mexicoas wellas in Eastern Africa showed me photographs which were seem­ingly taken in one and the saIl\elocality; only a very closeinspec­tion revealed that some of the pictures represented MexicanCacti and others East African Euphorbieae. If the two plants didnot occur in two differentcontinents, this resemblancewouldhavemade an ideal object for the supporters of the mimicry-theory.

Such outward resemblance is more probably due to analo­gous climatic and geographical conditions which tend to evolvecertain features best adapted to endure.

An interesting exahlple of similarity of appearance is,recorded on Plate 6, which shows a comparison of the growths ofMonadenium stapelioides (Euphorbiaceae), Huernia aspera(Asclepiadaceae), and of Notonia petraea (Compositae). Allthree plants occur in the vicinity of Nairobi on the same type ofrocky ground. The resemblance is confined to their outwardappearance, for they are not in the least related.

In spite of the frequent outward similarity of succulents ofdifferent origin, we find much diversity of appearance amongthem, though always on the lines of the one dominating prin­ciple: economy in water consumption. This aim is reachedmainly by reducing the surface of evaporation to a minimum,while preserving at the same time the chlorophyll-covered sur­faces which are essential for maintaining metabolism. Theoreti­cally the ideal Succulent would thus present a spherical shape,

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with its surface adapted for assimilation, and this extreme de­velopment has indeed been reached by certain globular Cactifrom Mexico, by the South African Euphorbia ooesa and by someSouth-West African Mesembrianthemum. spp.

Nature has, however, a variety of ways for achieving a

similar aim, and another trend of adaptation is represented inthe abovementioned "bushman's candle": here, the plant iscoated impermeably and has adapted itself in such a manner

that the rare emission of leaves after exceedingly long periodsof rest is sufficient to safeguard continuity of life.Other Succulents have solved their problem in other ways,

and we thus find that almost every part of the plant can be modi­fied for the storage of water. It follows that Succulents mayassume a very great variety of shapes: they may be classed intothe following main categories, although it is pointed out herethat this is by no means a scientific classification, its only purposebeing to illustrate the various forms which may be met with inEast Africa. On Plate 7 a typical representative of each of theseforms is shown.

Modified parts.

(1) Trunk only.(2) Trunk and branches only.(3) Branches and leaves (the latter

well developed).(4) Trunk and branches, while leaves are

greatly reduced and deciduous. Spinyor spineless. Inflorescence fleshy.Turning woody with age.

(5) Whole plant including inflorescencefleshy, without woody's~ructure.

Represented on Pl. 7 by

Cissus sp.Aden-iurn coeta1teumCotyledon. barbeyi

Euphorbia b"'1tll1t4 ar=

C;\l'aIlUlllJ ,UUll:rr~I1C,\ [m:SMeelie S9~Qtq

Although it might be tempting to base a description of Succu­lents on the above external characters, it will be more satisfac­tory and more instructive to describe them according to the placewhich they hold in the natural system, i.e. in their phylogeneticorder.

The families most prolific in succulent forms in East Africaate EUPHORBIACEAE and ASCLEPIADACEAE. Otherfamilies, like CRASSULACEAE and AIZOACEAE, thoughrepresented by numerous species in the South of the CClmtinent.are known by a few species only from East Africa, while GERA­NIACEAE, to which the above-mentioned "bushman's candle "belongs, have not produced outstanding succulent forms in ourpart of the world.

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COMPOSITAE.LABIATAE.LILIACEAE.ARACEAE.

MORACEAE ..ICACINACEAE.AMPELIDACEAE.APOCYNACEAE.ASCLEPIADACEAE.

On the other hand, some euphorbiaceous Genera, like Stena­denium, Synadenium, Monadenium, and Dorstenia are confinedalmost exclusively to Eastern Africa.

The following descriptions do not claim to include all Succu­lents to be found in East Africa; the flora of this country is fartoo imperfectly known for such an undertaking, nor has theauthor had access to all literature on the subject, and every yearnew species are discovered to increase an already great variety.This lack of completeness, however, adds rather than detractsfrom the charm· of this interesting group, for every lover ofnature has it within his reach to make discoveries of his own.

The aim of this paper is mainly. to stimulate the interest incollecting and cultivating East African Succulents, and to dis­prove the often heard contention that they cannot bear compari­son with those of other countries.

EAST AFRICAN SUCCULENTS ARRANGED IN THEm NATURAL ORDER.Families . Genera.

CRASSULACEAE.Cotyledon, Crassul~, Kalanchoe, Sed1.1ai.AIZOACEAE. Mesembrianthemum.PORTULACACEAE. Portulaca, Talinum.PASSIFLORACEAE. Adenia.CUCURBITACEAE. Momordica.CACTACEAE. Rhipsalis.EUPHORBIACEAE. Euphorbia, Monadenium, Stenadenitim,

Synadenium.Dorstenia.Pyrenacantha.Cissus.Adenium.Caralluma, Ceropegia, Cynanchum, Du­valia, Echidnopsis, Edithcolea, Huemia,Sarcostemma, Stapelia.Kleinia, Notonia, Senecio.Aeolanthus.Aloe, Anthericum, Bowiea, Sansevieria.Zamioculcas.

CRASSULACEAE. (Plate 8.)This family is .widely distributed over hot and temperate

countries. The centre of its distribution is in Africa, but repre­sentatives are found aiso in Australia and Polynesia, a very fewm South America.

In the Northern Hemisphere, including Europe, it is repre­sented by the· Genera Sedu'm and Sa:rlfraga.

The Genera found in East Africa are: Cotyledon, Crasittla.,Kalanchoe. Sedum.

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Cotyted01t.The genus is represented with over thirty spctCiesin South

Africa, while only two are known from East Africa.

Cotyledon Barbeyii, Schweinf.Has a wide distribution in East Africa, where it is endemic.

It has been collected from south of Kenla Colony as far north 1&Erythrea. It is one of the most ornamental of East AfricanSucculents, a vigorous shrub that may attain a height of sevenfeet. The erect branches bear large, fleshy, rounded leaves of afresh green, powdered with a slight waxy bloom. The flowersrise on a slendet stem in a graceful, somewhat drooping, cymeof bell-shaped flowers which range from a pale lemon-yellow tA>

a glowing vermilion.Plate 7 (3)-whole plant. Plate 8 (I)-flowering branch.

Cotyledon umbilicus, L.The distribution of this species is very wide indeed; it is

known to occur in Britain, in the Canary Islands, in North­Western Africa. In East Africa the plant has been found in thealpine zones above 10,000 feet of most of the higher mountains;it is a small, succulent herb, rarely over a foot in height. Thesmall, bell-shaped, flowers are greenish-white, standing outalmost horizontally from a single, sometimes branched, stem.which rises from a rosette of fleshy, disc-shaped leaves withnotched edges, attached to the stalks in the centre. The plantis not a, truly xerophyte, but seems to pre!er damp places; it isfound mostly on mossy rocks near mountam streams.

Crassuta ..More than two hundred species of the most varied appear­

ance are known from Southern Africa, while the species knoWR.from East Africa are far less numerous and in most cases lessshowy. They are small herbs, with few exceptions more thana few inches high, wi~h small, sometimes. minute, star-shapedflowers, which grow either singly- Qnslender stalks from the leaf­axils, or in dense clusters from a main stem.

Crassula abyssinica, A. Rich.Is widely distributed over tropical Africa. It is one of the

tallest and most robust member of the family, attaining a heightof 21 feet. The single stem, which is branched towards the top,carries a dense cluster of small, star-shaped, white or purple,flowers. The fleshy leaves are lancet-shaped and minutely saw­edged. They are arranged around the stem in such a way thatthe larger leaves form a kind of rosette at the base becoming lessnumerous and smaller as they ascend the stem. (Plate 8 (2a).)

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Cra8sula alsinoides (Hook f. Engl.).Was first discovered in Cameroon but was found later to

extend all over tropical Africa, including East Africa. It is aherb with fleshy, oblong leaves which are dotted with smallmaroon spots. The flowers are star-shaped, white, and some­what fleshy, and grow singly on slender stalks, from the leaf­axils. The plant grows seldom higher than about eight inches.Very nearly related to this species are:-

, Crassula, coleae, Bak., which is common on rocks in KenyaColony (Plate 8 (2b).);

Crassula galunkensis, Engl., with slightly narrower leaves;Cra8sula volkensii, Engl., from Lake Dschalla in Tanganyika,

a more robust species, growing to nearly a foot in height; andCraBsula nakurensis, Engl., which is found on rocks around

Lake Nakuru.

Cra8sula cra8sipes, C. A. Smith.Crassula pharnaceoides (Hochst.), Fisch. et Mey.Cra8sula parvijolia, E. A. Bruce, .and related species show yet another type of appearance: thesmall, narrow, fleshy, ,leaves are arranged very closely in oppo­site alternating pairs, which give the branches an outwardresemblance to club-mosses. None of them grow very tall; theyhave sometimes the appearance to miniature trees of less thana foot high and are quite ornamental in a rock-garden. Theflowers are minute and not showy. On Plate 8 (2c) a Cra8sulasp. belonging to this type is shown.

Cra8sula erubescens, Bullock, from Mt. Elgon, growing on rocks,is a very small herb, barely two inches high, with bright scarletfoliage; it has smallJ single, cream-coloured flowers.

Crassula aquatica, L. ,Cra8sula pentaneira, Boyle.Cra8sula. Wrightiana, Bullock.

All occur in E. Africa, they are also succulent herbs, but astheir habitat is mostly in swamps and bogs and in other dampplaces, they are outside the scopeof this paper, which deals withSucculents suitable for rock gardens.

KALANCHOE.This genus which is very rich in forms is distributed over

the tropical and sub-tropical parts of Asia and Mrica. It isrepresented by a number of very ornamental species in EastAfrica. They are sturdy, very succulent, herbs, s.ometimesattaining a height of six feet and over, growing often in clumps.

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PLATE 8.

FIG. 1. FIG. 2.

FIG. 3. FIG. 4.

CRASSULACEAE.

The fairly large four-petalled flowers grow in dense cymes on atall stem. Their range of colour is wide. White, cream, yellowin many shades, salmon-pink, brick-red, and scarlet-floweringspecies make Kalanchoe a desirable planUn rock gardens. Evenwhen not in flower, the fleshy, often showily marked leaves, arevery attractive.

Kalanchoe crenata, Haw.A tall, succulent herb up to 5 feet, which is widely distri­

buted over tropical Africa. The fleshy foliage is of a rich glossy,green, sometimes with a narrow maroon edge, the flowersprim­rose yellow. It is common around Nairobi and seems to preferthe light shade of forest edges and of high grass.

Kalanchoe glandulosa, Hochst.Common in the Ngong Hills on poor rocky soil, this plant

rarely attains a height of more than 16 inches. The radicalleaves at the base are no more than two inches long and !inchwide, and they diminish in size alolJg the stem of the plant,which bears a cluster of primrose-coloured flowers, rising fromfleshy, globula~, calices which are, like the rest of the plant,covered with fine, rather sticky, hairs. (Plate 8 (3).)

Kalanchoe glaucescens, Britt.One of the most attractive of indigenous Kalanchoes. It is

mostly found in clusters which present a most pleasing aspectwhen in full bloom. The medium-sized leaves have notchededges of a deep maroon, while their green surface is coveredwith a bluish-green bloom. The flowering stalks rise to a heightof over two feet where they form a mass of coral-red flowers.Though small in size individually, their number and. brightcolour, contrasting with the blue-green of the leaves, produce avery good effect. The plant is common in the Ngong Hills andon Lukenya, near Nairobi.

Kalanchoe lateritia, Engl.Not unlike in appearance from Kalanchoe glaucescens, this

species has smaller flowers with narrower petals, nor are theflowering heads so dense. The flowers are, however, more bril­liantly coloured, a bright vermilion. It prefers low and hotdistricts and is found in the country extending from Kilimanjaroto·the TeitaHiUs.

Kalanchoe Lugardii, Bullock.A tall, apparently widely spread, Kalanchoe, which attains

a height of over 5 feet. The flowers measure about one inch in

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diameter and seem to vary' much in colour, but pure white andyellow seem to be predominant. The leaves are large up to nineinches long and five inches wide, the notched margins markedwith maroon. The plant has been found from Mount Elgon at7,500 feet to Lake Rukwa in Tanganyika at various altitudesdown to 4,900 feet. (Plate 8 (4).)

Kalanchoe petitiana, A. Rich.Is very similar to Kalanchoe crenata, except that leaves and

all green parts are quite smooth. The distribution is approxi­mately the same.

Kalanchoe somaliensis, Baker.The giant of East African Kalanchoes occurs quite commonly

in Nairobi district on old cultivated land. It was probablyintroduced in Kenya by Somali cattle and horse dealers, and itis now firmly established here.

The large, pale-green leaves are mottled with maroon andthey cling to the thick, sturdy stalk at its base, rather in thefashion of cabbage leaves, while higher up they are set moreloosely in opposite pairs.

The flower heads are large, and so are the individual flowers,which are waxy-white and attain a diameter of 1i inches, theirtube being two inches long.

Kalanchoe sp.In the half-shade of shrubs and trees on the Ngong Escarp­

ment and on Lukenya behind Athi River station occurs aKalanchoe which differs from all others by its finely divided,though fleshy, leaf, which makes it an attractive plant in therock-garden. The flowers are small and ivory-white, and theyare set off very well by the brilliant emerald-green of the fleshyleaves and stalks.

SEDUM.The Genus is but poorly represented in East Africa, and

apparently confined to the higher regions.

Sedum ruwenzoriense, Baker.A small succulent herb of decumbent habit which grows

mostly epiphytically in trees or on mossy rocks. The leaves aredistributed loosely all along the stem; they have the size androunded shape of hulled rice. The flowers grow at the end ofthe branches in rather dense cymes. They are five-petalled starsof a brilliant golden yellow, and a plant in full bloom is a veryattractive sight ..

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Sedum Meyeri JohQ:nni8, Engl.from Mt. Kilimanjaro is a plant of appearance and habits

very similar to the above.This concludesthe descriptive list of the Crassulaceae which

are represented in the Herbarium of the Coryndon .MemorialMuseum, and although it is by no means a complete record ofall East African species, it is hoped that it will convey to thereader a fair idea of the appearance, the habits and the distribu­tion of this family without bothering him unduly with highlytechnical terms or descriptions.

(To be continued)

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